"We're doing what's called a grid search," said Cpl. Vickie Warehime, a police spokeswoman.
The officers, spaced about 100 yards apart, searched for Joseph Palczynski, who is accused of killing three people while abducting his girlfriend last Tuesday, and a fourth during a carjacking the next day.
"They're looking for him or evidence that he has been there."
Warehime did not disclose what led officers to search in the park, about two miles from the scene of three of the killings and the abduction.
Police said they have fielded more than 1,000 calls from people who say they've seen Palczynski, who was tracked back to their Baltimore County neighborhood after fleeing to Virginia, police said.
County police used an automated telephone calling system Sunday to provide 1,700 households in the Bowleys Quarters area with a description of Palczynski.
"Please lock your doors. Keep a lookout for a suspect matching the description. This suspect is armed," the recorded message reads.
The search for Palczynski, 31, was made difficult by his outdoor survival skills, and the acquisition of camping gear, said Baltimore County Police spokesman Bill Toohey. He was last spotted wearing woodlands camouflage clothing and was also believed to have a small, battery-operated television.
"He's an experienced outdoorsman. He's physically fit and seems to be comfortable out there," Toohey said Sunday.
A total of 100 people were dedicated to the around-the-clock hunt, in addition to dogs and thermal imaging equipment on board helicopters. Police were searching a circular area about 11 miles wide, Toohey said.
Residents of the area around Bowley's Quarters were shaken by news that he was still on the loose.
Mahmud Ashfaq, the owner of the Essex Tiger Mart, said one of his employees lives in the apartment building where George and Gloria Shenk were fatally shot Tuesday night.
"He says in the building, all the people are gone," Ashfaq said of his employee, whom he declined to name. "He says he is the only one there."
Authorities believe he made his way into Virginia late in the week. Baltimore County Police said he may have rode a freight train to just north of Richmond.
He is believed to have broken into an unoccupied home in southwestern Caroline County, Va., stealing a handgun, shotgun, and a pickup truck. When the truck later ran out of gas near Woodford, Va., he walked to a nearby house and forced a man at gunpoint to drive him back to Middle River, police said.
The man, William Terrell, told police they stopped along the way so that Palczynski could buy food and supplies, police said.
Toohey said Palczynski"seems to want to be close to those places he knows."
Palczynski's girlfriend, Tracy Whitehead, moved out of the apartment they were sharing earlier this month and in with Mrs. Shenk, with whom she worked. Four days later, Palczynski allegedly walked into the Shenks' apartment and shot the couple while taking Whitehead hostage.
Outside, Palczynski killed a bystander who tried to intervene as he took Whitehead to his car. The next day, he fatally shot a motorist while attempting to steal a car, police said.
Whitehead later escaped from Palczynski unharmed. She is currently in "a secure place," Toohey said.