Charges have been filed in the crash Friday night in Winter Haven that killed a Lake Wales man and his 4-year-old son.

William Monroe Gainey, 61, of Lake Wales was charged Monday night with two counts of DUI manslaughter, two counts of vehicular homicide and one count of DUI with property damage. He was already being held in the Polk County Jail on a domestic battery charge stemming from an altercation before the crash.

Investigators say air bag module data from Gainey's 2014 Chevrolet Silverado shows the pickup truck was traveling at 80 mph and accelerating when it slammed into the back of a 2010 Ford Focus at a red light on Cypress Gardens Boulevard. The driver of the Focus, Christopher Ivey, 38, and his young son Jayden were killed in the 10:30 p.m. crash.

Gainey was taken to Lakeland Regional Health, where tests showed he had a blood alcohol content of 0.74 percent and benzodiazepines (tranquilizers) in his system, investigators say.

According to the investigators' timeline, Gainey got into an altercation at his home on Silver Spur Loop with his girlfriend's son between 9:30 and 10:30 p.m. The son declined to press charges, but Gainey was charged with domestic battery against the daughter, who had attempted to intervene. The girlfriend told investigators Gainey had appeared "a little drunk" and "has been drinking more in the past four or five months when he started showing more depression," the arrest affidavit says.

The girlfriend's daughter told investigators she saw Gainey get into his truck to leave and that he was impaired when he left, the affidavit says.

Investigators say a witness reported seeing a truck with a driver matching Gainey's description swerving at a high rate of speed on Cypress Gardens Boulevard around 10:15 or 10:20 p.m. The witness said the truck hit a curb and almost flipped and, at one point, speed up and almost run into the back of a car.

Gainey's truck slammed into the back of Ivey's Focus with such force that it flipped onto its roof and traveled to 200 feet. The Focus was propelled about 190 feet into a ditch. Two witnesses who attempted to render aid to Gainey said he appeared intoxicated, investigators say.

According to the affidavit, Gainey casually told a Lakeland police officer as he was leaving the hospital Saturday he had been in a crash the night before and thought he had hit a tree. While being interviewed by an investigator later, Gainey said he had gotten into a fight with his girlfriend's son and the next thing he remembered was waking up in the hospital. Gainey told the investigator he knew nothing about a crash but admitted to drinking "three or four Budweiser beers" before it got dark.

The inconsistencies in Gainey's accounts were noted in the affidavit.

Investigators say the air bag module data shows that Gainey was traveling at 80 mph and accelerating .05 seconds before the crash. The data also showed that Gainey did not brake before the crash, and it recorded a "non-deployment event"  consistent with a curb strike before the crash.

Gainey was scheduled to make his first appearance on the new charges Tuesday afternoon.