A necropsy is underway to determine the cause of death of a 20-foot minke whale that came into Barnegat Bay over the weekend.

New video obtained by News 12 shows the whale thrashing and interacting with a pontoon boat before encountering a second boat, which resulted in one person going overboard.

New Jersey State Police say the whale charged at the vessel on Saturday. No one was hurt, but the whale did not survive.

Video taken from Miss Erin Fishing Charters shows the minke thrashing about after it entered the inlet. It’s then seen interacting with a pontoon boat. It happened at least an hour before the second encounter.

“It’s a sad and difficult situation for anybody in the marine mammal field,” said Dr. Danielle Brown, a leading expert on whale behavior in New Jersey and head researcher for Gotham Whale, and the Jersey Shore Whale Watch boat tours in Belmar.

“Necropsies are super important in this case. One, minke whales are under an unusual mortality event, so this is not the first instance stranding in this area. We want to learn why this is happening, why this is going on,” said Brown.

Brown says whales do not want to be in shallow water, and it was likely suffering from other issues before becoming stranded and eventually dying in the bay.

News 12 showed the new video to Jersey Girl Capt. Charlie Van Der Lynde and Jersey Shore Whale Watch owner Bill McKim.

“The boater probably didn’t do the greatest thing by being too close to it, but it was a sick whale and probably wasn’t going to make it,” said McKim.

McKim’s Jersey Shore Whale Watch follows federal guidelines, which means people must stay at least 100 feet away from whales. But if a whale comes toward a boat, McKim says to take the boat our of gear, shut the motor off and wait for the whale to leave the area.

A necropsy on the dead whale began Monday morning on the southern tip of Island Beach State Park. Results usually take a few weeks. The entire incident is still under investigation by the New Jersey State Police.

Those who see a whale in a bay or acting unusually are asked to call the Marine Mammal Stranding Center at 609-266-0538.