Philadelphia police are investigating an incident in which Electricians union leader John J. Dougherty allegedly hit a nonunion electrician in the face in an altercation at a worksite.

The nonunion contractor, Joshua Keesee, said that during the Jan. 21 incident in South Philadelphia, Dougherty broke his nose with one blow and hit him above an eye with another.

He said Dougherty lost his temper and swung first. Keesee said he then landed a blow, too, opening a wound in the head of a man who was with Dougherty.

In a statement Monday, a spokesman for Dougherty said the union leader had been involved in a "brief physical altercation" and "was not the aggressor."

The spokesman, Frank Keel, said Keesee had threatened Dougherty's family. When Dougherty confronted him verbally about that, he said, Keesee threw a punch at him.

"John Dougherty ducked the contractor's punch and countered with a punch to the assailant's face," the statement said. "That was the end of the incident."

Keesee's lawyer, Robert Mozenter, said detectives told him they had urged the District Attorney's Office to arrest Dougherty and the men with him on aggravated assault charges. But, Mozenter said, District Attorney Seth Williams instead referred the case to state Attorney General Kathleen G. Kane.

A spokesman for Williams did not return repeated calls seeking comment. Nor did the detective assigned to the case. A spokesman for Kane confirmed that the District Attorney's Office had contacted her staff to refer a criminal matter involving Dougherty.

He said it was unclear whether the office would accept the referral. "We are anticipating learning more in the next few days," Kane spokesman Chuck Ardo said.

Dougherty's spokesman said Monday, "We firmly believe that there should be no criminal charges filed in this matter, as John Dougherty acted purely in self-defense."

The fight broke out near Third and Reed Streets at a worksite for the construction of a dozen homes that has been controversial for its use of nonunion labor. Union forces have at times installed their giant inflatable rat at the site to call attention to the issue.

Keesee, 36, said the incident began about 8:15 a.m. He said Dougherty, 55, and three other men approached him to complain that he had a union decal on his truck.

He said Dougherty was pointing his finger and demanding that he remove the decal. "That's my sticker," he said Dougherty told him.

Keesee said he agreed to remove the sticker, but also challenged Dougherty verbally. "I was giving it right back to him," he said. "I was telling him, 'I'm not intimidated by you.' "

"He was starting to talk with me with clenched teeth," Keesee said.

Next, he said, Dougherty "just moved forward and threw a left-and-right combo."

The incident quickly devolved into a scrum, with Keesee absorbing blows as the men surrounded him.

Keesee provided video from a security camera outside a business on Third Street that he said captured the scene just minutes after the fight ended.

The video has an initial time stamp of 8:22 a.m. and is dated Jan. 21. It shows another worker on the job pulling Keesee away as Dougherty and three other men advance toward him.

In the video, a man standing beside Dougherty has blood near his left eye.

Keesee said he chose not to swing back at Dougherty because he was worried he would shatter the sunglasses the labor leader was wearing. He said he also took note of Dougherty's white hair and concluded he was elderly.

"I definitely didn't want to hit him. The first shot, I just took," Keesee said. "He hits me twice and they kind of converge on me."

Keesee acknowledged that he swung back, striking one of Dougherty's companions in the face.

A witness, James Yates, 64, said Monday that he watched the clash from the second-floor window of his house on Third Street.

Yates said the incident began with a verbal confrontation between Keesee and Dougherty and the labor leader's three companions. He said it appeared to escalate into violence when Dougherty and his group rushed toward Keesee.

"The four of them charged," he said.

Almost immediately, he said, he lost sight of the altercation because the men moved outside his field of vision.

Moments later, Yates said, Keesee came back into view, dashing across the street with Dougherty in pursuit. At that point, he said, he saw Dougherty throwing punches, but could not tell whether any landed.

Yates provided photographs he took showing Dougherty at the scene.

Keesee's lawyer, Mozenter, said Williams called him Friday to tell him he had referred the matter to state prosecutors.

The lawyer said Williams told him he once had "a run-in" with Dougherty and thus faced a conflict in handling the case.

"He said there was some bad feeling and he didn't want to give the impression he was persecuting him," Mozenter said.

Keesee said he was upset that Williams had passed the ball to another agency.

"I feel bad for the citizens because it's like people in power, people who are affluent, are able to escape," he said.

Court records show that Keesee was charged with aggravated assault and robbery in 2004, and the charges were dropped. On Monday, he said he had faced false accusations brought by the mother of his child.

Mozenter said he was preparing a lawsuit over the incident involving Dougherty.

Williams, like many in Philadelphia's political community, has a complicated relationship with "Johnny Doc" and his Electricians Local 98.

The union backed Daniel McCaffery, now a Common Pleas Court judge, in the 2009 Democratic primary for district attorney. Williams won that election.

In 2012, Williams was caught texting, "if u see Johnny Doc . . . watch your back" to a fellow Democratic politician. Dougherty later said Williams was suffering from "paranoia."

In 2013, Local 98 gave Williams' campaign $11,500, the maximum allowable annual contribution from a political action committee, as he ramped up to run for a second term. The union gave Williams' campaign $6,000 in 2014.

Records show that the union also gave donations to Kane: $20,000 in 2013.

215-854-4821@CraigRMcCoy

Staff writer Chris Brennan contributed to this article.