(CNN) Two dolphins were found shot and stabbed within a week off the Florida coast, and authorities are now looking for whoever is responsible.

At least 29 dolphins have been stranded in the Southeast since 2002, according to the National Oceanic and Atmospheric Administration (NOAA) Fisheries, with four incidents just last year. There is evidence they were shot by guns or arrows or impaled with objects like fishing spears, NOAA Fisheries said in a news bulletin Tuesday.

Biologists with the Florida Fish and Wildlife Conservation Commission discovered the first dolphin off of Naples late last week, according to NOAA Fisheries.

The dolphin died from what appears to be a bullet or sharp object wound, the bulletin said. That same week, Emerald Coast Wildlife Refuge researchers found a dolphin with a bullet in its left side along Pensacola Beach.

And in May, NOAA officials found a deceased dolphin off Captiva Island with a fatal puncture wound to its head.

NOAA officials are seeking any information from the public and are offering a reward of up to $20,000 for information that leads to a civil penalty or criminal conviction in the case.

Humans feeding wild dolphins may have made the animals associate people and boats with food, which could have put them in the position for someone to intentionally harm them, the bulletin said. NOAA Fisheries recommends people can help prevent harm by not feeding wild dolphins.