WASHINGTON – From the early stages of Wednesday’s hostage standoff in suburban Silver Spring, Md., tactical officers had positioned themselves to shoot James J. Lee. The big fear: Doing so would set off explosives attached to his body and kill his three hostages.

“It looks like he’s got a dead-man’s switch,” a bomb-squad member said into his radio, part of the stream of information being sent into a command bus 700 feet away.

“Frazier, he’s got a dead-man’s switch,” Assistant Montgomery Police Chief Drew Tracy said inside the bus. “What do you think about this pin?”

“That must be a positive safety,” responded Battalion Fire Chief Kevin Frazier, an explosives expert. “He’s using it as a safety.”

The snippet of conversation, recalled by both men Thursday, was part of the intense, split-second decisions made over nearly four hours Wednesday during the situation at the headquarters of Discovery Communications. Commanders, snipers and bomb experts had had to account for a children’s nursery on the floors above the suspect, had to evacuate the building through an opposite corner, had to figure out Lee’s explosives – all while trying to learn who he was and see into this mind, according to interviews with seven law enforcement officials who were inside the bus.

“We had quick information on the person, quick intel,” Tracy said Thursday. “His value of life was very low. He didn’t value his life or others’ lives.”

Also Thursday, new details emerged about the ongoing investigation and Lee’s bizarre past.

Bomb squad members searched Lee’s home in suburban Wheaton, Md., and found four additional explosive devices. Police also announced that Lee’s gun found inside the Discovery building was a starter pistol.

In 2003, according to court records, Lee was sentenced to 18 months in prison for trying to smuggle illegal immigrants into the United States. In recent years, however, Lee had begun calling immigrants “disgusting filth.”

2008, he had moved to the D.C. area. That year, he launched a protest outside the Discovery building, earning him a short jail stay for disorderly conduct.

He returned about 1 p.m. Wednesday, walking into the building’s large lobby, a room with glass on three sides, looking out onto sidewalks bustling with lunchtime pedestrians. He was armed with what looked like a gun and a contraption on his back. He took three men hostage, including a security guard positioned at a welcome desk.

It was a surreal setting. The lobby is designed to entertain visitors, with an exact replica of a Tyrannosaurus Rex. Discovery employees call him “Stan,” named after Stan Sacrison, who discovered the creature. A Triceratops sculpture sits nearby, as does a kinetic sculpture with moving gears and balls sliding down tracks.

Federal, state and local law enforcement converged quickly on the building. Montgomery County police parked their command bus on a quiet side street one block to the south. They began taking reports from officers who got close to the lobby or watched the building’s surveillance camera feeds.

One of their first decisions: Evacuate a day-care center of about 100 children, ranging from infants to 5-year-olds. The children were taken out a door on the far side of the building and shooed into a McDonald’s. More than 1,500 workers also were evacuated from the building.

Tactical teams, composed of SWAT officers and a bomb expert, moved in. They had been training together more regularly over the past year, a recognition that guns and bombs have gone hand-in-hand in recent high-profile cases.

Some of them got inside the Discovery building without Lee’s knowledge. Others positioned themselves just outside the lobby’s glass walls, taking cover behind landscaping structures, peering through binoculars.

There were compelling reasons to move in on Lee, authorities say. He repeatedly said he was willing to kill himself and take the hostages with him. There were boxes near him that the bomb technicians worried were something he brought in.

The shooting experts relied on the bomb experts trying to figure out what he had. At times, Lee removed a pin from a hand-held device, which looked like a detonator, and held it in what one officer described as a “death grip.” Then he’d put the pin back and move the device to his other hand.

A contraption on his back included four small tanks and pipes.

“He was making gestures as if he was attempting to set off bombs,” recalled Montgomery County state’s attorney John McCarthy. “A lot of really tough tactical decisions were being made.”

All the while, three hostages were lying on the ground nearby.

Taking in reports over the radio, Frazier – the explosives unit chief – drew sketches while inside command bus. “If he lets go,” he remembered telling others, “yes, potentially, the device could go off.”

“Without a doubt that was a major concern,” recalled Capt. Darryl McSwain, commander of the police department’s Special Operations Division.

As it turned out, the contraption was determined to be lethal: The tanks held propane, and the pipe bombs contained BB pellets that could have acted like shrapnel.

As Wednesday dragged on, there was a general feeling on the bus that time was on their side. Hostage negotiators spoke to Lee from a sectioned-off area of the command center, so Lee couldn’t hear background noises. Officers ate granola bars and gulped down bottles of water.

From the lobby, Lee told negotiators that he wanted to air grievances during a Discovery channel program. The negotiators told him they’d talk to the people at Discovery. They tried to humanize the hostages, whom Lee referred to as “parasites” at one point.

As much as they tried to control the operation, though, it was the actions inside the lobby that prompted them to move just before 5 p.m. According to McCarthy and others, two of the hostages appeared to try to make a run for the door. Tactical officers on the other side of a wall heard a “pop,” ran around the wall and saw Lee with a gun in his hand. At least two of them fired. “Had they simply wanted to shoot him and kill him, they could have done it hours earlier,” McCarthy said.