Just how deadly a killer is marijuana? Here's a GIF showing all of the people who have died after overdosing on pot:

Yeah, not a single person has ever died from a weed overdose. We don't have numbers on pandas, but we're guessing it's about the same. According to one frequently cited study, a marijuana smoker would have to consume 20,000 to 40,000 times the amount of THC in a joint in order to be at risk of dying.

Last week, Attorney General Eric Holder announced that the federal government wouldn't intervene as Colorado and Washington state implement plans for a system of legalized marijuana for adults. The decision opened the floodgates for other states to pursue similar legalization efforts and outraged police groups apparently not excited to see a shift away from the failed war on drugs.

In a joint letter written to Holder on Friday, law enforcement organizations warned that his move would lead to more crime, violence and even death.

While high driving may be a concern, Colorado, Washington and federal authorities have all taken steps to keep people off the road after using marijuana. The two states both have their own restrictions, and Holder said in his statement that the DOJ would still prosecute individuals or entities to prevent "drugged driving."

The police groups also make a number of additional controversial claims that marijuana use itself leads to violent behavior, suicidal thoughts and interest in harder drugs. Scientific studies have not been able to prove this causation conclusively, however, and research has also suggested that THC has significant therapeutic value to patients suffering from cancer, AIDS or glaucoma.