Ricky Best was stabbed to death last Friday on a Portland light-rail train when he and two other passengers tried to calm a man yelling anti-Muslim slurs at two teenage girls.
Best and the two other stabbing victims have been hailed as heroes.
Now, Portland police say that as Best lay helpless, someone apparently made off with his wedding ring and backpack.
Police posted images of the suspect on YouTube and Twitter late Thursday, along with a plea for the public's help in locating him, reports Washington Post.
"The contents of the backpack include personal items important to the Best family," said a police statement, which described the suspect as a "white male with a blonde hair mullet, wearing a black Jordan Brand baseball cap, a black T-shirt featuring an image of Marilyn Monroe and an American flag, black shorts, and black shoes."
Best, 53, an Army veteran and Portland city employee, was on his way home when he and fellow passengers, Taliesin Myrddin Namkai Meche, 23, and Micah David-Cole Fletcher, 21, intervened after a man began yelling slurs at the teens, one of whom wore a Muslim head covering.
The man then turned his anger on those who tried to help, fatally stabbing Best and Meche and injuring Fletcher.
Police later arrested Jeremy Joseph Christian, 35, in connection with the killings. Christian appeared in court on Tuesday, but did not enter a plea.
He has a history of making bigoted comments online and in local publications. The Southern Poverty Law Center described him as a "known white supremacist."
Tension has run high in Portland lately due to clashes between black-clad "antifa," or anti-fascist activists and right-wing protesters with ties to white nationalist movements, The Washington Post has reported.
After the commuter train killings, Mayor Ted Wheeler asked the federal government to bar rallies planned by two right-wing groups at a plaza under its jurisdiction.
The mayor and others also hailed the actions of the men who intervened on the train.
"Two men lost their lives and another was injured for doing the right thing, standing up for people they didn't know against hatred," Wheeler said in a statement. "Their actions were brave and selfless, and should serve as an example and inspiration to us all. They are heroes."
With his voice breaking, the mayor said of Best: "He was an Army veteran killed on Memorial Day weekend."
Police spokesman Pete Simpson said that the men had been attacked "viciously" by the suspect as they were trying to "de-escalate him and protect some other people on the train."
Best, a resident of Happy Valley, Ore., was pronounced dead at the scene, police said. He was married with three teenage sons and a 12-year-old daughter, according to the Oregonian. His funeral is set for Monday at Christ the King Catholic Church in Milwaukie, Ore.
In 2012, he retired from the Army as a platoon sergeant after 23 years in the military that included service in Afghanistan and Iraq, according to the Oregonian.
"He was always cheery," his oldest son, Erik Best, told KATU. "After serving in the military, he'd usually say, 'Hey, I'm not getting shot at, why shouldn't I smile?'"
At the time of his death, he worked as a technician for the Bureau of Development Services. "He was always the first person you would go to for help," his supervisor, Kareen Perkins, told the Oregonian.
His sister, Arena Best, told Oregon Public Broadcasting that it was just like her brother to come to a stranger's defense.
"I don't even think he hesitated," she said. "He was always a hero."