A Montgomery County police officer and a security man were killed yesterday when they were surprised by burglars shortly after 7 a.m. at a catalogue discount store in White Oak.

A manager for the W. Bell & Co. store also was critically wounded as he and the others checked the building after at least two burglar alarms had been activated.

County police said they were looking for a dark subcompact car in which two suspects fled after the killings of Police Officer Philip Metz, 33, and David Wayne Myers, 30, a security employe for the burglary alarm company.

Douglas Cummins Jr., 28, of Vienna, Va., a manager at the Bell store at 11130 New Hampshire, remained in critical condition last night after surgery for gunshot wounds.

Details of the killings were sketchy, but it appeared that Metz and Myers were gunned down in an office where the store's safe was located. Cummins had been handcuffed to a file cabinet and shot, according to sources, and apparently was left for dead by the burglars. However, he managed to call police and drag himself out a side door of the building.

Metz, a nine-year veteran on the force, was the tenth Montgomery County police officer slain in the line of duty since the department was organized in the late 1920s. His death comes five years almost to the day since the last two county police officers were killed while trying to apprehend a bank holdup suspect.

The events that led up to yesterday's double slaying began at 6:16 a.m. when Electro Protective Corp., an alarm company, called police to say that an alarm had gone off at Bell, according to a police spokesman. Minutes later, a Wells Fargo alarm also went off in the store.

Sometime after the first alarm and before 6:30 a.m., a police officer from the midnight shift had checked the store, found no signs of forcible entry and left. Officer Rick Nelson, a midnight-shift officer who was patroling his nearby beat, said he heard that officer announce on the radio "Disregard. It's tight. I'm going back to the stable" -- meaning that he had checked the outside of the store and was going back to the Silver Spring station to end his shift.

Police spokesman Nancy Moses said that officers would not enter a store unless there are signs of forcible entry or they have reason to suspect that someone is inside.

But at 6:55 a.m., Electro Protective, under a routine procedure, called county police asking for an officer to join their security man and a Bell manager in checking the inside of the store. Officer Metz, who was just coming on duty, was dispatched on that call.

It is unclear precisely what happened next, except that Metz and the others apparently met in front of the store and went in a side entrance.

A backup officer, John Wilkes, arrived at the store about 10 minutes later, found Metz's squad car outside, checked the entrance and tried unsuccessfully to raise Metz on a portable radio. He also spent several minutes checking the registration of a Cadillac parked in the store's lot. Wilkes, assuming that the three men were still checking the store, radioed in to the dispatcher and left the scene, according to police.

However, within five minutes, the wounded Cummins called police and an "officer shot" radio dispatch set off various squad cars, their sirens blaring, speeding to the Bell store.

The first officer to arrive found Cummins outside the side door, where he had dragged himself after pulling out a file drawer to which he had been handcuffed. Inside the store, the officer found Myers, shot in the chest, and Metz, apparently shot in the head, according to investigators.

Deputy Medical Examiner John Rogers said that because of the type of wound Metz suffered, he could not be certain if he had been shot until after an autopsy.

Officer Nelson, who rushed to the store with scores of other off-duty officers, said that so many false alarms go off each night that "when you get an alarm and you don't have a hunch something's wrong, you get lax. It just happens."

Spokesman Moses said that 22,000 burglar alarms went off in the county last year, 98 percent of them false alarms.

The suspects apparently entered the store by cutting a hole in the roof at the back of the structure. Electricians working in a partly completed building next door to Bell's said one of their coworkers saw two men run across the parking lot after 7 a.m., rush through the woods and get into a small, dark-colored car, possibly a Honda, and drive off.

One officer at Bell's said the shooting occurred at the time of day when there are the fewest police officers on the street. "There are not enough officers on the shift," the angered policeman said yesterday. "That's the worst part."

The county police have recently gone into a new shift system under a plan to place more officers on the street between 10 a.m. and midnight. Moses said this is the department's peak period for calls, and that 7 to 10 a.m. is one of the periods when it received the fewest calls. The plan has been criticized by the county's Fraternal Order of Police, which plans to picket the county office building in protest next week.

But Capt. Owen Bromley, who heads the Silver Spring station where Metz was assigned, said yesterday that anyone who says a different shift system could have prevented the shootings is "just speculating."

Officer Metz was single and lived in Germantown. Myers, who was also single, lived with his parents in Wheaton.