That report said the animals were down the road on Baltimore Street, which is Pa. 16 inside the borough limits.
A borough police officer said the animals were in town only for a few minutes before they were chased into Antrim Township.
"We tried just about everything we could. This thing was huge," Pennsylvania State Police Trooper Jeremy Matas said.
He said the cow was shot at least twice with tranquilizers, but the drugs didn't seem to have an effect.
Matas said he shot the cow at about 9:30 p.m. at a construction site off Moss Spring Road.
"We didn't want to do it this way, but it was getting dark and we couldn't have it running around," he said.
The cow damaged a chain-link fence in the borough, but Matas was unaware of any other property damage.
The effort to round up the two animals involved three state troopers, about four borough police officers, and firefighters, farmers and livestock auction employees, Matas said.
Greencastle Rescue Hose Co. Chief Robert Ebersole said fire police from his company and Marion were on standby along Interstate 81 in case the animals got onto the highway.
McNew said the 565-pound steer was tranquilized and returned to the sale barn shortly before 9 p.m. Matas said the steer was caught off the interstate near the northbound weigh station.
McNew estimated the cow weighed more than 1,000 pounds.
Matas said he believed borough police called in experts with the tranquilizer guns, but did not know who they were.