SAN FRANCISCO (CBS SF) – Two 21-year-old suspects have been arrested in the vicious, 2014 beating death of a disabled 67-year-old homeless man in San Francisco that was caught on video, authorities said.

Investigators said the suspects attacked Tai Lam twice between 11 p.m. and midnight in an alley in the 100 block of Sutter Street on November 23rd. Lam, who weighed less than 100 pounds and stood about 5-foot-5, was found in his sleeping bag and taken to San Francisco General where he died of his injuries.

The arrest came after nearly two years of investigative work by San Francisco police detectives and an evidence hit on a nationwide DNA database.

Police were also aided by security camera video that clearly captured the images of the three suspects wanted in the beating case.

Authorities said Joseph Stull was in custody Kootenai County, Idaho on grand theft, possession of stolen property and other charges when detectives learned of a match to his DNA from evidence collected at the San Francisco crime scene.

Authorities said that in September San Francisco detectives flew to Idaho to interview Stull. The suspect reportedly gave the investigators explicit details about stomping death.

According to the San Francisco Examiner, Stull allegedly told the detectives the attack was completely random.

The three beating suspects were captured on security camera video as they smoked a cigarette on the steps to Crocker Galleria near Montgomery and Post streets shortly after the attack.

With information gathered from Stull, San Francisco detectives were able to track down David Peters in Stockton.

In a joint operation with Stockton police, a local home was searched last Friday and evidence linking Peters to the crime was discovered. He was taken into custody.

Both Stull and Peters have been booked into San Francisco County jail on murder, robbery, elder abuse and mayhem charges.

Investigators were asking anyone with information on this case to contact the San Francisco Police Tip Line at (415) 575-4444 or Text-a-Tip to TIP411 and begin the text message with SFPD.

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