There is nothing in your link about his mother saying he had not been hit with a fire extinguisher.His mother talked to him and she determined he was not hit with a fire extinguisher.
I'll even use a shitty source in the hopes it will better convince you.
PolitiFact - Update: Capitol police officer Brian Sicknick died of natural causes
New information from the chief medical examiner for the District of Columbia provides fresh details that call into questwww.politifact.com
EMTs on scene reported they suspected a head wound. They found him struggling to breathe...which is why they also suspected exposure to bear spray.
EMS report reveals ‘suspected exposure’ evident when they responded to Capitol officer who died
New details are emerging on Friday about the death of a U.S. Capitol police officer who died after an attack on the Capitol building earlier in the week.
www.fox10phoenix.com