(NewsNation) — A retired U.S. Marshal said a note that officers discovered Thursday could have answers about the ongoing search for the man they say opened fire in two buildings in Maine.

Officers discovered the note while using warrants to search several properties, Maine Department of Public Safety Commissioner Michael Sauschuck said. Investigators haven’t disclosed the contents of the note or its potential relevance to the investigation.

It’s possible it contained details authorities could use to help inform their search for the alleged gunman, said retired U.S. Marshal Art Roderick.

“To me, that note might be the key to this whole thing because it could indicate motive,” Roderick told “NewsNation Now” Friday. “It also could indicate possible suicidal intentions which might have brought them back to the boat dock.”

Investigators haven’t said if or how the note has helped their search, which entered its third day Friday.

“It could have also taken them back to the boat dock to look for possibly something he might have thrown in the river,” Roderick said. “Maybe he got rid of some evidence or even possibly committed suicide in that area, but it sounds like they haven’t found anything up to this point.”

Police have been searching for Robert Card, the 40-year-old Bowdoin, Maine, resident they believe is responsible for the shooting since Wednesday night.

The situation began when a man with a gun walked into a bowling alley in the town of Lewiston and opened fire, killing seven people.

One eyewitness, Kenny Moore, said the shooting likely ended quickly after the shooter’s AR-style rifle seemed to have jammed, causing him to flee.

Less than 15 minutes later, gunfire broke out at a billiards bar 4 miles across town, killing 11 more people, according to authorities.

Police since then have focused their search near the Lisbon boat dock where they discovered the alleged gunman’s vehicle. Several additional searches are underway throughout town.

The Maine State Police issued a warrant Thursday for Card’s arrest on eight counts of murder. More counts are expected, pending the identification of 10 victims.

Meanwhile, Maine’s hunting season was slated to begin Friday. Roderick cautioned against entering the state’s dense, wooded areas with a weapon with a manhunt underway.

Authorities have since announced hunting is prohibited in Lisbon, Lewiston, Bowdoin and Monmouth.