A gunman who set off a smoke grenade injured at least 29 people, 10 of whom were shot, on a rush-hour subway train in Brooklyn Tuesday morning just blocks from the Nets’ training facility as they prepared for their play-in game against Cleveland. The manhunt for the shooter snarled traffic and had police helicopters flying overhead.

“It’s obviously a very tragic morning. We’re devastated for the community and those directly involved,” Nets coach Steve Nash said at the team’s morning shootaround before Brooklyn’s 115-108 play-in victory over the Cavaliers. “I don’t know all of the details so I don’t want to get too far into it. But we’re just all concerned for everyone involved [and will] try to prepare for the task at hand the best we can.”

The suspect started the mayhem around 8:30 a.m. on a Manhattan-bound N train at the 36th Street station.

“They always text us when there’s traffic and get there little early, but I didn’t know the specific reason until I got into the building,” Kevin Durant said. “You see the helicopters … outside. You just want everything to work out and figure it out.

“They sent us a text to say there might be some traffic, but I didn’t know why. And then you look through your phone and see stuff. I hate violence. I hate senseless violence and hopefully we can figure out the details and get everybody to safety and get everybody the help that they need. But it’s a tough situation right now.”

The HSS Training Center is just a half-mile away — roughly five blocks — and a number of Nets staffers take the subway. All were accounted for Tuesday morning, and preparations for the Cavs went ahead as scheduled, albeit with something of a pall caused by the tragic and ongoing situation around the corner.

“Guys pretty much heard stories on social media through their phones and hopefully they get this figured out and people safe. I know there’s a couple people shot. It’s just an unfortunate situation and I hope they get it figured out,” Durant said.

“It’s devastating to hear about. … I don’t know too many details, but to hear the sirens out front of the practice facility and see so much commotion going on outside, you hope and pray for the best for everybody involved.”

The Nets security team — led by Fred Galloway — informed Nash. But with players coming from all different places and arriving at different times, canceling shootaround at that point was impractical.

For example, Goran Dragic — who had cleared health and safety protocols and was available to play Tuesday night — was at the facility bright and early before the incident.

“I heard. I was already here. I didn’t even know the players were talking about it, about shooting in the subways,” Dragic said. “It’s terrible. I just hope nobody is hurt bad and everything is going to be well.

“I get here around 9, 8:45. I was in my car. Five people got shot, something like that? So yeah, I’m just praying for the families that everybody is going to be OK and resolve this thing.

“I was just talking to [assistant] Jordan Ott the coach and we were talking about the situation and he was saying, ‘You see that yellow building? That’s where that happened.’ So it’s really close. It’s kind of scary of how close. And I’ve already been in the subway a couple times, but now I have my doubts.”

The Nets had a moment of reflection before tip-off on Tuesday night. The team announced in coordination with its sister club the Liberty — both owned by Joe Tsai — a joint donation of $50,000 to helping victims of the subway shooting.

Ben Simmons (sore back) has made more progress over the past week than in the first three weeks after his epidural.

But when asked about The Athletic’s report that the All-Star could be ready by Game 3 of the first round if the Nets advance, Nash said, “I have no idea. I don’t know where these reports come from. We have no update on the timetable so I don’t think that came from us.”