Cops say they’ve collared Fort Greene gunman — well, one of them at least!

Police arrested a gunman who went on a robbing spree in Fort Greene Park last week, but another armed thug is on the loose — a sign that crime isn’t slowing down in the idyllic greenspace.

Cops arrested a 49-year-old man on Sept. 10 in connection with three stickups, but the next day, a different lunatic tried to rob a Brooklyn Hospital nurse at gunpoint as she took a break in the park.

Brooke Steven said she was near Willoughby and St. Edwards streets at 3:15 pm when the perp flashed a gun and demanded cash. He fled without harming her.

“It was sunny out and there were all these kids running around — and this guy comes out of nowhere with a gun,” Steven said. “Honest to god, I thought he was joking.”

Deputy Inspector Anthony Tasso, the 88th Precinct’s commanding officer, said he will boost patrols near St. Edwards Street to prevent more muggings like the spate last week, half of which occurred in broad daylight with children and families nearby.

“We’re working with detectives to see what’s going on — if the suspect has a partner or a brother that looks a lot like him,” Tasso said.

The spike in park robberies started this summer, when thieves plucked people’s phones during the day and pummeled victims at night. It was enough for cops to increase patrols and for a local karate instructor to teach women self-defense in the urban oasis itself.

But muggings have been rampant both inside and within blocks of the park despite police promises of increased surveillance.

Last week, the arrested suspect attacked park-goers at least three times, cops said:

• He first ambushed three people on Sept. 5 near the Prison Ship Martyrs Monument at 8 pm.

Sara Thompson, a 22-year-old Manhattanite, was with her boyfriend and a friend at when the goon came from behind, flashed a gun and swiped $200.

“This guy was so nonchalant about it and telling us to hurry up or he was going to blow my friend’s head off,” Thompson said. “It was unbelievably real and very scary that he did it in front of everyone.”

• On Sept. 6, he jumped a 30-year-old woman at St. Edwards Street and Myrtle Avenue at 9:30 pm, taking her jewelry and cash.

• On Sept. 9, he attacked a woman on a bench at St. Edwards and Willoughby streets at 3:50 pm and took $44.

Tasso said the suspect was arrested after “a very strong ID was made out of a mug books.” But Thompson believes the guy who attacked her is still out there — she couldn’t identify him in a lineup.

“This has definitely changed my mind about moving to Fort Greene,” Thompson said. “Sometimes it’s just not as safe as you would think.”

According to NYPD data, there were 33 robberies in Fort Greene and Clinton Hill over the last month, compared to 16 during the same period last year.

— with Thomas Tracy