PLEASANTON -- The father of a teenage driver suspected of fatally hitting a Dublin bicyclist last month was arrested Thursday after police found illegal weapons in his house while serving a search warrant on his son, authorities said.

Officers served the warrant on 18-year-old Cody Hall in hopes of finding evidence that may contribute to the investigation into the death of 58-year-old Diana Hersevoort, according to Pleasanton police Sgt. Mark Reimer.

Police said that about 1 p.m. June 9, Cody Hall hit Hersevoort with his car as she was riding her bike with her husband on Foothill Road about a quarter-mile south of Golden Eagle Way.

Cody Hall was the only one home when officers arrived at the residence in the 4200 block of Echo Court on June 30, Reimer said, and while searching the house, they found a large gun safe in the garage, to which Cody Hall said he did not have the combination.

After officers were unable to get anybody to come home and open the safe, they forced their way in and found two illegal assault rifles and thousands of rounds of ammunition. Further investigation revealed that the gun safe belonged to Cody Hall's father, 43-year-old Aaron Hall, a twice-convicted felon who is prohibited from having any firearms in his possession, Reimer said.

While he would not speak to the nature of Aaron Hall's past felony convictions, Reimer said they were charged in 1993 and adjudicated in 1994, the year Cody Hall was born. Court documents indicate those convictions were for assault with a deadly weapon and firing at an inhabited dwelling.

Court documents also indicate that Aaron Hall had recently tried to purchase another firearm but had been turned down due to his criminal convictions.

Officers also confiscated from the safe four Daytrana patches, an amphetaminelike medication used to treat ADHD, that Aaron Hall had without a proper prescription, according to court documents. Officers found no weapons in Cody Hall's possession, and none of the evidence taken from him was of a criminal nature.

"We did collect some things related to his case, but they're requiring further analysis," Reimer said. "There wasn't any contraband as far as Cody was concerned."

Pleasanton police handed Aaron Hall's case to the Alameda County District Attorney, who charged Aaron Hall with several felony charges, including being a felon in possession of firearms and ammunition and being in possession of illegal assault weapons. He turned himself in Thursday after officers obtained a $640,000 warrant for his arrest.

Aaron Hall was booked into Santa Rita Jail, where he later posted a reduced bail of $265,000 and was released that same day, Reimer said.

"I can't speculate as to what kind of punishment he will face or what time he would serve," Reimer said. "I would expect that it would be counted in years, not months."

Cody Hall's case remains under investigation by the Pleasanton Police Department's traffic division, which is handling the case separately from his father's. Aaron Hall is scheduled to be arraigned July 24 at the Gale Schenone Hall of Justice in Pleasanton.

Contact Erin Ivie at eivie@bayareanewsgroup.com. Follow her at Twitter.com/erin_ivie.