Authorities in Massachusetts now suspect that the grim tally of victims linked to an already-convicted murderer has doubled.

Kevin Lino, 38, who is currently serving a life sentence alongside a concurrent 40-year term for the murders of two men in 2012 and 2014, faces new allegations. In August, the Middlesex District Attorney’s office brought charges against Lino for the deaths of two additional men, dating back more than a decade.

The new charges have prompted law enforcement to apply a rarely used and chilling designation.

“Mr. Lino is a serial killer,” District Attorney Marian Ryan stated in a conversation with Boston 25 News. She further explained, “The Department of Justice defines a serial killer as someone who has taken the life of two individuals in separate incidents. In this case, we already have convictions for two murders. We have now filed charges for two more.”

In a pattern reminiscent of his prior convictions, Lino was charged earlier this year with the murders of two additional men, both of whom, like his earlier victims, were experiencing homelessness. Despite these charges, Lino has pleaded not guilty.

In its August announcement, the district attorney’s office said investigators uncovered evidence that Lino beat Gary Melanson, 54, to death with a baseball bat at a Lowell homeless encampment in 2010. 

The other accusation surrounds the 2012 death of Douglas Leon Clarke, 30, which was previously seen as an accidental overdose and no foul play was suspected. 

The district attorney now claims new evidence links Lino to Clark’s death, with investigators discovering they had been living in the same homeless encampment in Cambridge.

Investigators, per the statement, now believe Lino killed Clark by intentionally injecting him with a fatal dose of heroin—commonly referred to as a “hot shot.” They also learned, according to the statement, Lino was angry with the heroin users who were living at the homeless encampment.