Killer whales have gone crazy off the coast of Monterey Bay in California, and scientists are trying to figure out way. The orcas are reportedly going on a killing spree, and have gotten their fourth kill in the last few days after weeding out a gray whale calf and separating it from its mother.

Scientists say the spree is “unprecedented,” and in this case a whale-watching tour got to see the action up close. The incredible video of the encounter is embedded at the bottom of this post.

“This has never happened in my thirty years,” Nancy Black, a marine biologist with Monterey Bay Whale Watch, told The San Francisco Chronicle. “Just to witness that out in nature when you usually see that kind of thing on television is really spectacular.”

Orcas usually take hours to kill a grey whale calf, usually because it’s hard to get the mother to back off. But in this case it only took them 20 minutes to tackle their prey.

The whales were reportedly thinner than usual, which may explain why they couldn’t put up much a fight. A total of nine killer whales killed the calf.