Six dead cats were found over a 15-day span on the Howard Frankland Bridge earlier this summer. Then earlier this month, a driver spotted a seventh cat: a survivor.

A small black-and-white kitten was seen rolling out from underneath a pick-up truck on Aug. 7, a driver told the Florida Highway Patrol. The truck was going at least 70 mph and didn't stop.

The cat now called "Miracle" was rescued from the bridge with just a scratch. But the incident fuels a growing bay area mystery: who is dumping cats onto the Howard Frankland?

"The whole thing is fishy," FHP Sgt. Steve Gaskins said. "But I don't have any more to go on."

The FHP is hoping a $5,000 reward will change that.

A St. Petersburg animal activist is offering the reward money to anyone who can provide information leading to the arrest and conviction of whoever is leaving cats on the bridge.

READ: Dead cats keep showing up on the Howard Frankland Bridge

Meow Now told the FHP that its founder, Dan Hester, would supply the reward money. The nonprofit works to spay, neuter and vaccinate stray cats in Pinellas County to control population.

"I suspect someone is throwing cats out of a vehicle," Hester said, "and getting some kind of kick watching them get run over."

READ: Meet Whiskers, the cat rescued after it tumbled from a car on the Howard Frankland Bridge

Gaskins announced the award Tuesday on Twitter. By Wednesday troopers had gotten a few calls, but nothing that explains what's been happening on the bridge.

Investigators have no evidence linking the incidents together, Gaskins said. Nor do they know if Miracle was thrown from a vehicle or fell out of one — but the latter scenario seems unlikely.

Gaskins doesn't believe what happened Aug. 7 was an accident. If it wasn't deliberate, the sergeant said, then Miracle's previous owner would have come forward by now to claim their cat, especially after all the media attention.

"Do I think it's suspicious? Yes," he said. "I would know if I had a cat in my car, and if the cat came out of the vehicle, I think I would notice."

Another indicator that these are deliberate acts is that there's a pattern to where the cats were found: on the left side of the northbound span, approaching the hump.

"I'm hard-pressed to believe a cat would walk up either side, two, three, four miles, all the way over to the middle of the bridge in all the traffic," he said.

The driver who witnessed the Aug. 7 incident only caught a glimpse of the pick-up: it appeared to be an old brown truck with a shiny metal topper.

Gaskins hopes the reward will make drivers "more likely to keep their eyes open" on the Howard Frankland. They can call FHP by dialing *347 on their cell phones as soon as they see something strange.

Have info regarding cats left on the HFB? Call *FHP w/ Tips. $5000 reward now offered for info leading to arrest."There's a whole bunch of variables here," Gaskins said. "But you know, I'd love to put an end to it if I can."Hester said the thought that someone is intentionally endangering cats on the bridge keeps him up at night."By putting the money up, I'm hoping someone comes forward," he said.pic.twitter.com/XZ9eAXLXCl— Sgt. Steve Gaskins (@SteveG717) August 16, 2016

Have info regarding cats left on the HFB? Call *FHP w/ Tips. $5000 reward now offered for info leading to arrest.

"There's a whole bunch of variables here," Gaskins said. "But you know, I'd love to put an end to it if I can."

Hester said the thought that someone is intentionally endangering cats on the bridge keeps him up at night.

"By putting the money up, I'm hoping someone comes forward," he said.

pic.twitter.com/XZ9eAXLXCl

Contact Sara DiNatale at sdinatale@tampabay.com. Follow @sara_dinatale.