Please. You don't know this. For all you know, the ducks got in front of the car and wouldn't move. Maybe after a few minutes of this he got tired of it, had to go to work, had to pick up his kid, etc. It was just a few ducks. Bravo Foxtrot Delta.
He couldn't have been "too late for work" or whatever, if he had time to also get out and chase several ducks down to kill with his bare hands.
As to "no evidence" or "no studies" liking animal cruelty/torture to crimes against human, here's some anecdotal evidence, and a link or two. You can google mre, if you really wish to; this was just a quick, sloppy search to get a few examples. I'm sure if you really wanted to see any evidence, you could easily find it.
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"Some of the most striking evidence for a link between animal cruelty and human violence lies in the case histories of many of the 20th century's most infamous criminals."
"Mass-murderer and cannibal Jeffrey Dahmer killed neighbors' pets and impaled a dog's head on a stick."
"Patrick Sherril, who murdered 14 co-workers and then killed himself, stole pets, then tied them up and allowed his own dog to mutilate them."
"David Berkowitz, the so-called "Son of Sam," shot his neighbor's labrador retriever."
"Albert DeSalvo, the "Boston Strangler," shot arrows into boxes of trapped cats and dogs."
"Brenda Spencer, who fired 40 shots into a crowd of children, murdering 2 and wounding 9, had a history of setting the tails of neighborhood cats and dogs on fire."
"Edmund Emil Kemper III, who murdered his mother and 7 other women, used to abuse cats and dogs."
"Carol Edmund Cole, who murdered 35 people, admitted that his first violent act was strangling a puppy."
"Richard Allen Davis, kidnapper and murderer, doused cats with gasoline and set them on fire."
"Studies of prison inmates reveal that as many as 75% of violent offenders had early records of animal cruelty. There is also a high correlation between family violence and animal cruelty. A study in 1983 of New Jersey families referred to youth and family services for reasons of child abuse reported that 88% of cases had at least one member of the household who physically abused animals. An English researcher found that 83% of families reported for animal abuse also had children listed at high risk of abuse or neglect."
http://www.arkonline.com/violence.html
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“Murderers ... very often start out by killing and torturing animals as kids,” according to Robert K. Ressler, who developed profiles of serial killers for the Federal Bureau of Investigation (FBI). Studies have now convinced sociologists, lawmakers, and the courts that acts of cruelty toward animals deserve our attention. They can be the first sign of a violent pathology that includes human victims.
Animal abuse is not just the result of a minor personality flaw in the abuser but rather a symptom of a deep mental disturbance. Research in psychology and criminology shows that people who commit acts of cruelty toward animals don’t stop there; many of them move on to their fellow humans.
The FBI has found that a history of cruelty to animals is one of the traits that regularly appear in its computer records of serial rapists and murderers, and the standard diagnostic and treatment manual for psychiatric and emotional disorders lists cruelty to animals as a diagnostic criterion for conduct disorders.
A study conducted by Northeastern University and the Massachusetts SPCA found that people who abuse animals are five times more likely to commit violent crimes against humans. The majority of inmates scheduled to be executed for murder at California’s San Quentin penitentiary “practiced” their crimes on animals, according to the warden.
http://www.helpinganimals.com/a-abuse.html