The man accused of killing his cellmate at the Downtown Detention Center this week has an extensive criminal history, including multiple previous arrests for assault, attempted murder and driving under the influence.

And investigators in Aurora are also looking into whether the suspect is connected to two fatal stabbings on Sunday.     

Rick Roybal-Smith, 38, faces a new first-degree murder charge after Denver Sheriff’s Office deputies found a man unresponsive in a unit at 2:48 a.m. on Monday morning, according to a Denver Police Department news release.

Denver police arrest Downtown Detention Center inmate accused of killing cellmate

A Denver Sheriff’s Department deputy was alerted by Roybal-Smith at about 2:15 a.m. that his cellmate needed help, according to a probable cause affidavit for his arrest. As deputies responded, they found the cellmate laying on his bunk, covered to his neck in a blanket and unresponsive.

The initial investigation revealed red marks on the cellmate’s neck consistent with strangulation, the affidavit said. A detective tried to interview Roybal-Smith about the incident. The latter was advised of his constitutional rights.

Roybal-Smith had been booked into the center the previous day after allegedly hitting two pedestrians with his Cadillac at the intersection of North Galapago Street and West 9th Avenue in Denver while under the influence of drugs, according to a probable cause affidavit for that arrest. He fled the scene, only to be later tracked down and detained by police.

While police detained him, an officer observed that Roybal-Smith had red, bloodshot and watery eyes, slowed reaction time and a delayed response in ability or willingness to answer questions, the affidavit said.

The incident, which occurred around 2:40 p.m. Sunday afternoon, occurred just hours after two men were found suffering from fatal stab wounds within a few blocks of each other in Aurora. The men, who appeared to be homeless, died from their injuries at the scene.

Police believe that Roybal-Smith is also connected to the twin killings, 9News reported on Tuesday.

2 deadly Aurora stabbings near Colfax are 'likely connected,' police say

“Based on the timeline, proximity of locations, and similarities in injuries, investigators now believe the two incidents are connected,” Aurora police officials said in a news release about the fatal stabbings.

Colorado court records showed Roybal-Smith previously pleaded guilty to a vehicular assault-DUI charge and was sentenced to 12 years on Oct. 6, 2016.

In June 2022, after his release on parole, he was arrested again on a weapons violation in Arapahoe County, according to the records.

He was sentenced to four years in prison after pleading guilty to the weapons charge.

The October 2016 sentencing stemmed from an incident that began at about 10 a.m. on Dec. 20, 2015, when police were called to the 5300 block of South Elati Street in Littleton on a report of a suicidal man, according to an affidavit for that arrest.

Roybal-Smith’s roommate had called police after he woke up to find him covered in blood with cuts on his neck and arms.

When police arrived, they saw a car registered to Roybal-Smith driving away, and they chased him, the affidavit said.

Roybal-Smith led police to the 4100 block of South Santa Fe Drive, where, while moving at about 72 miles per hour, he drove into the back of a car stopped at the intersection’s red light, a collision that resulted in the occupants of the car suffering serious injuries, with several broken bones and torn ligaments.

Roybal-Smith later tested positive for amphetamines at the medical center, according to the affidavit.

The 2022 incident, meanwhile, occurred on June 21, just before 1 p.m., in a Walmart in the 600 block of Englewood Parkway in Englewood, when Roybal-Smith reportedly approached a family shopping in the hunting and fishing department and said to the male, “If you’re a real man you’ll show me your balls right now,” according to an arrest affidavit for that case.

The man allegedly removed himself from the conversation, but as the family was checking out, Roybal-Smith approached him from behind with a 12 to 16-inch filet knife, the affidavit said.

The man’s fiancée, believing Roybal-Smith was going to stab him in the back, then grabbed her own pocket knife and brought it to Roybal-Smith’s neck, yelling at him to back away.

At about 3 a.m. the following morning, police caught Roybal-Smith while responding to a call of a woman screaming for help near the Englewood Civic Center, according to the affidavit. Witnesses had observed a man next to the woman. Officers chased the man, eventually detaining and identifying him as Roybal-Smith.

During the investigation into the death at the detention center, police concluded that the victim had been assaulted and identified Roybal-Smith as the suspect, according to authorities. The two shared a housing unit at the center.

The Denver Gazette’s news partner 9NEWS and reporter Noah Festenstein contributed to this article.