Opening of "Lifebuoy"

I just realized I forgot to post the beginning of my new story in On Spec, "Lifebuoy." Here it is.

What a mess, Karen thought as she saw the cluster of cruisers, all headed for the scene, getting in each other’s way as they tried to park. She shook her head, turned off the kojak wailing on top of her Tactical Unit van. A standoff during the hottest month of the year; everyone’s nerves would already be frayed, especially whoever was inside, and it wouldn’t take much to turn this into a shootout.
One of the cruisers was parked sideways in front of the door to the apartment building, and she saw a uniform crouched behind it, probably the guy who had called her team in. "Stay here," she said to Tim, got out of the car.
The cop behind the car turned her way. "About time you got here," he said, without too much rancor -- uniforms always resented having to call in Tactical, but it was nothing personal.
"What’s the situation?"
"Supposed to be a routine arrest," the cop said. He had a soft face and an attempted mustache. "I guess the guy saw us coming, started taking potshots out the window." He pointed up to the third floor.
She nodded. The building was a grey concrete block, each apartment dotted with a cheerless balcony. She knew the layout inside by heart: all the city-built housing used the same floorplan. "Handgun?"
He shook his head. "Hunting rifle."
Karen looked over her shoulder at the cruisers with her team inside, waiting for her instructions. "Your partner’s watching the other exit?" The cop nodded. She waved for her team, pointed out the first two to reach her. "You two reinforce the back exit. Everyone else, we’re going in. Draw weapons, check your tech."
She watched carefully as her team adjusted their vests, lowered their helmet visors and freed the Glock pistols at their belts. She wiped the sweat from her forehead and did the same. "Okay, everybody synch in."
Phil, one of her vets, frowned. "It’s gonna take at least a minute to get inside, K, and three to do the stairs."
"He’s shooting out the window, and he’s got decent range," Karen said. "That first minute’s going to be the most dangerous." She could see Phil chewing his lip through his visor, but he didn’t say anything more. "Tim, do the honors."
Tim opened the case he was carrying, drew out the buoy. It was about a foot long, black metal and plastic; it looked more like an oversized socket wrench than anything else, featureless except for the switches, one green and one red. "Ready," Tim said as he flicked the green switch.
Karen watched for the green flash from each of her team members’ shields that would show they were synched, then nodded. "Let’s go," she said.
Tim flipped the red switch and the buoy disappeared, stuck in that moment like a fly in amber. Karen checked her watch, set to count down. The tether back to the buoy was ten minutes long; if anything went wrong during that time she could trigger it, bring them back to this moment and avoid making the same mistakes.