There is a “strong probability” that Dayton mass shooter Connor Betts cased the Oregon District bar that he was running toward when cops gunned him down amid his rampage, police said Tuesday.

Surveillance video released by Dayton police shows that Betts, 24, left Blind Bob’s Bar then spent 30 minutes at Ned Pepper’s bar across the street before returning to his car for his gear.

“Whether he had gone in Ned Peppers to case it, I think that’s strong probability,” Dayton Police Chief Richard Biehl said during the press conference. “This was planned well before he got to the Oregon District.”

Biehl also said it was “inconclusive” whether Betts’ sister, Megan — one of the first three people he killed — was an intended target. He said police investigators were “divided” on whether or not she was.

The news came as police released a timeline of the mass shooting and new details about the killer’s Aug. 4 massacre — including that Betts body armor was “vulnerable,” making it easier for cops to shoot him.’

According to the timeline, Betts arrived at Blind Bob’s bar with his sister and Charles Beard, a friend of the siblings, at 11:04 p.m.

The trio socialized until 12:13 a.m., when Betts left and walked to Ned Pepper’s by himself, remaining there until 12:42 a.m. There is no indication he had a beef with anyone inside, cops said.

Betts then walked back to his car in the parking lot behind a Heart Mercantile retailer store, opened the trunk and retrieved his AR 15-style rifle and body armor, cops said.

Betts then spent nine minutes in a dark alley not covered by area surveillance cameras — likely loading the 100-round magazine he used amid the slaughter, Dayton Lt. Paul Saunders said.

Moments later, he can be seen reemerging and opening fire near a taco stand on 5th Street, video shows.

“He shoots round that corner pretty quickly,” Saunders said.

He moved walked east while firing and police gunned him down as he was chasing fleeing passersby into Ned Pepper’s.

Police later found drug paraphernalia in his car, but did not provide details.

Biehl said the case is now being turned over to the FBI for further investigation.

Dayton City Manager Shelly Dickstein said 14 separate local, county, state and federal agencies responded to the scene of the massacre.