The Denver Police Department received a tip last January about the man who went on a fatal rampage last week in Denver and Lakewood that left five people dead and two others injured, the department said in news release late Tuesday.

An investigative source who wished not to be identified confirmed to The Denver Gazette late Tuesday that a man named Andres Thiele contacted them from Wolfsburg, Germany, concerned that Lyndon McLeod might commit a “terrorist attack.”

“We are looking into how this was handled and what we could have done differently,” said the source, who admitted that police knew about McLeod’s million-page trilogy naming two of the five victims he eventually killed.

“When do you look at a work of fiction to see … is there something here?” the source asked.

The source said there were two separate investigations into McLeod at the time: One by the Denver Police and a parallel federal operation.

In Tuesday’s news release, the department said it received a tip that cited “several concerns” about the eventual shooter. The tipster warned police about a potential theft and fraud incident involving someone outside Colorado, according to the release.  The news release did not mention terrorism.

The release said investigators could not link the shooter to a Denver address associated with the tip and had “no reason to believe (McLeod) was living in Denver.” Additionally, investigators could not establish a Denver connection with the victim.

The release did not disclose any additional information regarding other concerns disclosed in the tip.

Police said there was not sufficient evidence to file criminal charges or a legal basis for monitoring McLeod at the time.

The release came after The Denver Post posted a story saying that Thiele had contacted Denver 311 on Jan. 3, 2021 saying that there was a “small, but undeniable possibility” that McLeod might “commit a terrorist attack.”

Thiele said he became alarmed after participating in an online chat with McLeod and fans of McLeod’s self-published books. The Post reported that Thiele said he also submitted a tip to the FBI and mailed them a letter.