The missing Alexandria activist whose body was recovered from a well in Fort Washington on Saturday had been shot to death, authorities said Monday.

Homicide detectives have not determined exactly when and where Lenwood “Lenny” Harris, 53, was slain, though they believe he was killed soon after he disappeared in September, Prince George’s County Police Chief Mark Magaw said at a news conference. Magaw said Harris’s body was dumped down the well on a vacant property in the 11900 block of Old Fort Road after he died.

An anonymous 911 call tipped detectives to the body Thursday, authorities said. That launched a days-long excavation process that ended Saturday when evidence technicians brought Harris’s remains above ground.

Detectives are still working to track down suspects and a motive in the case. They seem to have several leads: A tattooed man was caught on an ATM surveillance camera using Harris’s bank card hours after he disappeared, and police found Harris’s cellphone on the Woodrow Wilson Bridge.

Harris, who lived with his wife in Del Ray, was well known for popping in on Alexandria City Council meetings to discuss issues and city recreation centers to help kids. He made an unsuccessful run for the council in 2007 and co-founded the nonprofit Operation H.O.P.E., which offers mentoring and career development services. He also ran a pest-control business.

Tony Suggs, a longtime friend of Harris who was among the last people to see him alive, said he didn’t know “what to say or what to think” about the fact that his friend was killed. He said he knew Harris as a strong leader who helped Suggs personally in his battle to stay off drugs, and he hoped others would continue the work that Harris started.

“I just feel as though we lost a good community leader,” Suggs said. “But Lenny’s time here hasn’t been in vain because he laid a lot out. He did a lot of positive things throughout the community.”

Magaw said Monday that investigators were working to identify the 911 caller. He said whoever dumped the body in the well “obviously knows the area,” because it is secluded and the home on the property has been vacant since 1996.

Prince George’s County homicide detectives are working with Alexandria police.

At Monday’s news conference, Alexandria Police Chief Earl Cook said that he knew Harris personally and that his thoughts were with the activist’s family.

“Mr. Harris actually greatly affected Alexandria,” Cook said.

Harris was last seen Sept. 21 at the Charles Houston Recreation Center in Alexandria, Cook said. Suggs, who talked with him there, said Harris seemed mostly normal, although later, when detectives talked to him about his friend’s cellphone use that evening, it struck him that Harris seemed to check his phone frequently.

A reward of up to $38,000 is being offered for information that leads to an arrest and conviction in the case. Those with information are asked to call the Prince George’s police homicide unit at 301-772-4925.

Staff writer Allison Klein contributed to this report.