A fist bump. Then a fist fight. Then, witnesses say, a deadly daytime stabbing on Fisherman’s Wharf.

A fight between two men last week at San Francisco’s Fisherman’s Wharf ended with one of the men fatally stabbing the other in broad daylight and in front of several witnesses, prosecutors said.

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Appearing in court for arraignment Tuesday morning, suspect Bruce Penn, 56, pleaded not guilty.

Penn’s been charged with murder for the stabbing that killed Brook Pettyjohn, 44, last Wednesday at Taylor and Jefferson streets, near the iconic Fisherman’s Wharf sign.

Penn is being represented by the San Francisco Public Defender’s Office and is set to return to court on April 19.

According to court documents, after initially receiving numerous 911 calls about a stabbing, officers responded to the scene at 1:45 p.m. There they found Pettyjohn lying in a pool of blood, unresponsive. Suffering from multiple stab wounds, Pettyjohn was rushed to the hospital, where he died.

After interviewing more than 15 witnesses and checking surveillance video, investigators learned that Pettyjohn had gotten into a physical altercation with Penn moments before the stabbing.

Initially, the two men allegedly fist-bumped each other. However, Penn appeared to get mad when Pettyjohn placed his arms around Penn to “bearhug” him, court documents said.

Penn then allegedly punched Pettyjohn and also kicked him at least once. Pettyjohn did not strike back and fell to the ground, according to court documents.

When Pettyjohn got up, Penn allegedly “squared-up” toward Pettyjohn. But still Pettyjohn refused to engage and even tried to walk away from the fight, court documents said.

Penn then allegedly retrieved a machete-like knife from a nearby bag and walked up to Pettyjohn and stabbed him in the abdomen. As Pettyjohn stumbled backwards, Penn moved in closer and slashed Pettyjohn’s body, according to court documents.

The knife appeared to enter Pettyjohn’s body underneath his armpit, traveling through the center of his body. As Pettyjohn continued to stumble, blood squirted from his wound, and he ultimately fell to the ground, court documents said.

Officers were able to catch up with Penn at Taylor and North Point streets, just two blocks from where the stabbing occurred, and arrested him. According to police, both Penn and Pettyjohn frequented the Fisherman’s Wharf area, however it was not immediately clear if they knew each other prior to the fight.