Denver prosecutors said Tuesday they will not file charges against a 17-year-old boy arrested in connection with the slaying this month of taxi driver Darren Bloomquist.

Authorities say, however, they are still investigating the case and could file charges later.

“Were declining to file charges against him at this time,” said Lynn Kimbrough, spokeswoman for the District Attorney’s Office. “He was arrested based on probable cause, but our filing standards are that we need to be able to prove (guilt) beyond a reasonable doubt.”

Kimbrough did not elaborate on why prosecutors declined to file charges.

The teen, who has not been identified, remains in custody Tuesday in an unrelated case, officials say.

Bloomquist, 49, was shot to death Sept. 5 in the area of 20000 E. Mitchell Place in the city’s Green Valley Ranch neighborhood.

The teen was arrested Sept. 10 in west Denver on an unrelated warrant, police said. Officials declined to say what that warrant was.

“He was in custody when he was identified as a suspect,” Doug Schepman, a police spokesman, said earlier.

Bloomquist was a psychologist who moonlighted driving a cab for Metro Taxi to help pay bills after his wife was disabled. He was also an Air Force veteran who served at Travis Air Force Base.

Dozens of Denver taxi drivers gathered Friday at a memorial service for Bloomquist outside Metro Taxi’s offices. One by one the cabbies — and some of their wives — paid their respects and joined in solidarity to recognize the inherent dangers of their vocation.

The slaying put the city’s safety measures for cab drivers in the spotlight.

Security cameras have been shown to reduce the number of murders of cab drivers in cities where they are in common use. The cab that Bloomquist was driving, like many of those in Denver, didn’t have one.

Bloomquist was at least the eighth cab driver killed on the job in Denver since 1972, according to a list of slain drivers compiled by Taxi Library.

Arrest documents in the case have been sealed.

Jesse Paul: 303-954-1733, jpaul@denverpost.com or @JesseAPaul