A deeply mentally ill man who was implicated in a violent spree in the Tenderloin last spring that ended in a 15-hour standoff with police was killed Tuesday afternoon in a shooting in the Bayview neighborhood.

32-year-old Thomas O'Bannon was found suffering from a gunshot wound on Tuesday on the sidewalk of the 1300 block of Keith Street around 4:30 p.m. As Bay City News reports, police responded to the scene after a ShotSpotter detector alerted them to a shot fired in the area.

O'Bannon later died from his wounds at the hospital. No suspect has been arrested, but the SFPD says the suspect was a man in his 20s or 30s.

O'Bannon made headlines in April 2020 after he barricaded himself first inside a Tenderloin hotel lobby and then inside the offices of Glide Memorial Church, leading to a 15-hour standoff with police.

O'Bannon was being sought on the morning of April 21, 2020 after reportedly striking a pedestrian in the face with a board on Post Street, and then causing a scene in the lobby of the Pierre Hotel at 540 Jones Street. Police arrived at the hotel to find O'Bannon combative, swinging a board at them and then threatening them with a screwdriver. He then escaped out a back door, allegedly lunged at officers, and ran into the Glide building.

An SFPD officer discharged his weapon during the ordeal, but no one was injured.

O'Bannon then remained barricaded inside Glide until late that night, when he surrendered to police without further incident.

As KTVU reported in July, O'Bannon was actually on a 5150 psychiatric hold just the night before, on April 20, after apparently threatening neighbors and violating social-distancing rules at the Aranda Residence at 64 Turk Street.

When police arrived to arrest him, he reportedly said, "You’re going to have to kill me. You’re going to have to shoot me."

He was deemed a threat to himself and others and forcibly sedated at St. Francis Hospital, but inexplicably he was deemed no longer a threat by around 5 a.m. the next morning. No sooner had he been released, but the Post Street assault occurred around 5:40 a.m., and then the melee at the hotel.

Police later released images from the hotel encounter.

"It’s terrifying," said District 6 Supervisor Matt Haney at the time. "People who have deep mental illness – who have been 5150’d – should not be released back on the street without any sort of referral or oversight. In fact, it sounds like he definitely should have been kept longer."

Anyone with information about Tuesday's shooting on Keith Street is asked to call the Police Department’s tip line at (415) 575-4444.

Related: Knife-Wielding Man Reportedly Barricaded In Glide Memorial Church After Police Shoot At Him