William Abrams never felt in danger sleeping on his bedroll in hidden alleyways or along one of the city's viaducts. That all changed last week.

The discovery of the bodies of two homeless men in a manhole south of downtown on Jan. 9 made Abrams uneasy. The discovery three days later of two more dead homeless men in a manhole less than a block away scared him and others living on the city's streets.

"We don't know why these deaths took place. We don't know what was behind it," said Abrams, who worked as a semitrailer driver until problems with alcohol and drugs sent him to the streets seven months ago. "We don't know whether it was random or a serial killer.

"So, yeah, it is something to be aware of when you're walking past a corner somebody can hide at or even up under the viaduct. Just trying to be out at night is a fear right now."

Investigators don't believe the deaths are the work of a random serial killer and are working under the assumption someone had a motive to kill the four men, police Capt. Phil Trent said.

All four died of blunt force trauma, and Trent said there is little doubt they are related. "It's just too coincidental for it to be anything else," he said.

Trent said all four men were known to collect scrap metal from vacant buildings and elsewhere to sell — a subculture fueled by high aluminum and copper prices across the country.

But homeless people in the city say that doesn't make them feel any safer.

"The deaths definitely makes you more wary of what is going on," said James Harris as he stood with his belongings Tuesday outside the Hope Rescue Mission. "I worry about that every day."

The four deaths come as a shock in a city that had 11 homicides last year, Trent said.

He said after the bodies of Michael Nolen Jr., 40, and Michael Lawson, 56, were found on Jan. 9, investigators knew Brian G. Talboom, 51, was missing. The bodies of Talboom and Jason Coates, 29, were found three days later. No other reports of missing homeless people have been filed, Trent said.

To try to calm fears at the Center for the Homeless, where all four men had stayed, officials had a police officer speak to residents about safety, said Steve Camilleri, the center's executive director.