LOUISVILLE, Ky. >> U.S. Sen. Rand Paul does not know why a longtime neighbor tackled him in his yard and broke five of his ribs, sidelining him from the Senate, a close friend of the lawmaker said today.

Rob Porter, who says he has known Paul for 20 years, visited the senator on Saturday just one day after the attack. He said Paul was mowing his yard and had stopped to remove a limb when 59-year-old Rene Boucher, Paul’s neighbor for 17 years, tackled him from behind, slamming him to the ground. Porter said Paul was wearing ear protection and did not hear Boucher coming.

For days, mystery has swirled around what led to the assault, from Washington, D.C., to the high-end gated community where both men live. Rumors spread in the community that the attack stemmed from a festering neighborhood dispute about lawn debris. But Porter said in all the years he has known Paul, he has never heard him mention Boucher or any type of yard issue with his neighbor.

“Rand doesn’t really have any interaction with the guy. If there was a dispute, I do believe Rand wasn’t aware of it,” Porter said. “I have been to their house socially and for a variety of reasons for going on 20 years, I’ve never heard (Paul) mention (Boucher), good or bad.”

The FBI is investigating the assault to see if it was politically motivated. Boucher’s attorney, Matt Baker, said the attack had “absolutely nothing to do” with politics but was “a very regrettable dispute” that was “trivial.” He would not elaborate, saying he needs to “do my due diligence” before offering specifics about the case.

Paul’s representatives have declined to comment about what might have prompted the attack. Doug Stafford, Paul’s senior adviser, called the case a “serious criminal matter involving state and federal authorities.”

Baker said Boucher was uninjured. The attack broke five of Paul’s ribs, preventing him from returning to the Senate this week. A senior adviser said it’s unclear how long Paul will be out of work, noting his injuries could cause life-threatening complications if not treated properly.

Paul’s Republican colleagues in Washington were updated today about the Kentucky lawmaker’s condition, and the injured senator received a call from Vice President Mike Pence.

While attending the Senate GOP’s closed-door, weekly luncheon, Pence mentioned he had called Paul, and “the chuckle was that he must be OK because he was already working (Pence) on ideas on tax relief,” said North Dakota Sen. John Hoeven, who spoke to reporters afterward.

Boucher was released Saturday from the Warren County Jail on a $7,500 bond. A judge ordered Boucher to stay away from Paul and his family, a decision Baker said was routine in such cases. With Paul still recovering at his home, U.S. Capital Police have met with Baker to discuss security.

“They were just needing to satisfy themselves that going forward that there would not be any security issues,” Baker said.

Police charged Boucher, 59, with misdemeanor fourth-degree assault with a minor injury. He has not returned multiple calls seeking comment and did not answer the door when a reporter knocked on Monday.

Paul is an ophthalmologist and Boucher is an anesthesiologist. Baker called them “both prominent members of the medical community” who “worked together when they were both practicing physicians.”

Porter said Paul was “in pretty good spirits to be in as much pain as he was.”

“It’s hard to move around, you can’t sneeze,” he said. “Rand is a really tough guy. You’ve seen that in his (politics) and that’s the way he is personally. He is just, you know, he’s just going to make it through this.”

Associated Press Writer Kevin Freking in Washington contributed to this report.