It is unclear just when Powell learned that the kidnap plot had turned to an assassination. There is testimony from the nurse attending the Secretary of State indicating that Powell may have learned of his role to assassinate Seward on Thursday, April 13. A man fitting Powell's description appeared at the Seward home that day to inquire about the Secretary's health. Powell himself was inconsistent. He once said he learned he was to kill Seward on the morning of Friday, April 14, but later claimed he did not know until the evening of April 14. On the afternoon of April 14, Booth learned that Abraham Lincoln would be attending a play at Ford's Theatre that night. Booth decided that the time had come to kill Lincoln. Booth sent David Herold to tell Powell the news. Booth and Powell probably spent the afternoon and early evening at the Canterbury Music Hall on Pennsylvania Avenue, where Powell met and possibly had a tryst with Mary Gardner, a performer there. At 8:45 p.m. that night, Booth, Atzerodt, Herold, and Powell met in Powell's room at the Herndon House in Washington, D.C., where Booth assigned roles. They would strike that very night, Booth said. Powell (accompanied by Herold) was to go to the home of Secretary of State William H. Seward and kill him. Atzerodt was to assassinate Vice President Andrew Johnson. Booth was to murder Lincoln at Ford's Theatre.
The attack on Seward after attempting to shoot him At about 10:10 p.m., the same time Booth made his way to the unguarded presidential box at Ford's Theater, Powell was escorted to the Seward residence on
Lafayette Square near the White House by David Herold. Seward had been injured in a carriage accident on April 5, and suffered a concussion, broken jaw, broken right arm, and many serious bruises. Local newspapers reported that Seward was at home convalescing, so Powell and Herold knew where to find him. Powell was armed with a Whitney revolver and large knife, and wore black pants, a long overcoat, a grey vest, a grey dress coat, and a hat with a wide brim. Herold waited outside, holding Powell's horse. Powell knocked and rang the bell, and the door was answered by
William Bell, Seward's African American
maître d’hôtel. Holding up a small bottle, Powell claimed that Seward's physician, T. S. Verdi, had sent some medicine to the house. Bell was suspicious, as Verdi had departed the home only an hour earlier and left instructions for Seward not to be disturbed. Bell asked Powell to wait, but Powell pushed past him and began mounting the stairs to the second-floor bedrooms. Seward's son,
Frederick W. Seward, appeared at the top of the steps. When Powell reached the second floor, he told Frederick that he was delivering medicine, but Frederick refused Powell's request. As Lewis Powell and Frederick bickered over the medicine story, Seward's daughter,
Fanny Seward, stuck her head out of her father's bedroom door and warned the men that Seward was sleeping. She then returned to the bedroom. Once Fanny went into her father's bedroom, Frederick asked Powell to leave. Powell was about to take a few steps, but he pulled out his revolver and pulled the trigger with the barrel of the gun against Frederick's head. The revolver misfired, and Powell
pistol-whipped Frederick, beating him bloody and knocking him to the floor unconscious. Bell fled the house, screaming "Murder! Murder!", and raced to the office of General
Christopher C. Augur next door for help. Powell's pistol-whip attack on Frederick left his revolver completely broken, useless. Thus, in a rage-fueled frenzy, Powell drew out his knife and burst through Seward's bedroom door. Inside were Seward's Army nurse,
Sergeant George F. Robinson, and Fanny Seward. Powell slashed Robinson on the forearm, and the soldier fell; Powell pushed Fanny aside and leapt onto the bed. He savagely began knifing Seward in the face and throat. Seward, however, was wearing a metal and canvas splint on his jaw, which deflected most of Powell's blows. Powell nonetheless managed to cut through and slice open Seward's right cheek and along the right side of his throat, causing a large amount of blood flow which Seward began choking on. Believing Seward to be dead, Powell hesitated. Meanwhile, terrified by Fanny and Bell's screams of "Murder!", Herold fled on his own steed, leaving Powell on his own to escape from Seward's mansion. At 10:15pm, just as Booth mortally wounded President Lincoln at Ford's Theatre, Seward's other son,
Augustus Henry Seward, burst into the room. Powell stabbed him several times after Augustus dragged Powell onto the floor. Robinson and Augustus Seward wrestled with the strong, uninjured Powell. Powell stabbed Robinson in the shoulder and
slashed a portion of Augustus' scalp from his head, before making his escape. Powell was confronted by State Department messenger Emerick "Bud" Hansell in the hallway. Hansell had just arrived at the house moments earlier and found the front door ajar. As Hansell turned to flee, Powell stabbed him in the back. Powell ran down the stairs and out of the house, still in a fit of rage, yelling "I'm mad! I'm mad!" Then he threw his knife in the gutter of the street, got onto his waiting horse, and disappeared through the night.
Flight and capture Powell now realized that David Herold had abandoned him. Powell had almost no knowledge of the streets of Washington, D.C., and without Herold he had no way of locating the streets he was to use for his escape route. He mounted his horse, and began riding at a relatively slow pace north on 15th Street. Powell's exact movements from the time he was seen cantering up 15th Street until the time he appeared at the Surratt boarding house three days later are not clear. It is well-established that he ended up (by riding or walking) in the far northeast part of the District of Columbia near
Fort Bunker Hill, where he discarded his overcoat. In the overcoat pockets were Powell's riding gloves, a false mustache, and a piece of paper with Mary Gardner's name and hotel room number on it. Sources differ widely on what happened. Historian Ernest B. Furgurson says Powell's horse gave out near Lincoln Hospital (now
Lincoln Park), a mile east of the
United States Capitol on
East Capitol Street. He then hid in "a cemetery" (without specifying which). Ownsbey says Powell hid in a tree for three days. Historians William C. Edwards and Edward Steers Jr. claim Powell made it to both Fort Bunker Hill and
Congressional Cemetery (at 18th and E Streets SE), while Ralph Gary claims that Powell hid out in a marble burial vault at Congressional Cemetery. Andrew Jampoler, however, says Powell just wandered the streets of the city. Whether Powell abandoned his horse, was thrown by it, or both is unclear, and Powell never gave a public or formal statement about what happened. Powell decided to return to Surratt's boarding house to seek help. His clothes were somewhat bloody from the attack at Seward's home, and he had dropped his hat at the Seward home. During much of the
Victorian era, it was considered unseemly for any man (even a menial laborer) to be seen in public without a hat, and Powell would have been viewed with suspicion had he tried to enter the city without one. Ripping the sleeve from his undershirt, Powell placed the sleeve on his head in the hope that people would think it was a
stocking cap. To complete his disguise as a common laborer, he then stole a
pickaxe from a farmyard. Powell then headed for Surratt's. Members of the
Metropolitan Police Department of the District of Columbia already suspected John Surratt of complicity in Lincoln's murder, and had visited the Surratt boarding house for the first time as early as 2:00 a.m. on April 15, less than four hours after the attacks. Nothing incriminating was found. Federal authorities decided to make a second visit. Military investigators arrived at about 11:00 p.m. on Monday, April 17, to bring Mrs. Surratt and others in for questioning. As they were about to depart at 11:45 p.m., Powell showed up on the doorstep. Powell claimed to be a menial laborer who had been hired that morning by Mrs. Surratt to dig a gutter in the street. He explained his arrival at the house by saying that he wanted to know what time he should begin work in the morning. His clothes aroused intense suspicion, as he wore rather good quality boots, pants, dress shirt, vest, and coat. His pickaxe seemed unused, and his hands were uncalloused and well manicured (unlike those of a common laborer). Mary denied knowing him. She would later claim that her extremely poor eyesight and the darkness of the room prevented her from recognizing Powell. Powell stood under a bright lamp just five feet from her when she made her denial. Taken into custody, Powell was discovered to have a box of pistol cartridges, a compass, hair
pomade, a brush and comb, two fine handkerchiefs, and a copy of his oath of allegiance (signed "L. Paine") in his pockets. These were not the possessions of a menial laborer. Although he claimed he was a poor man who barely earned a dollar a day for ditch-digging, Powell's wallet contained $25 (~$ in ). About 3:00 a.m. on April 18, William Bell identified Powell as the man who assaulted Seward. Powell was formally arrested, and imprisoned aboard the , a Union
monitor then at anchor in the
Anacostia River at the
Washington Navy Yard. A second identification was made around mid-morning on April 18 when Augustus Seward visited the
Saugus and positively identified Powell as the man who attacked him and his father. ==Trial==