Why Does Islam Ban Images of the Prophet Muhammad?

On May 3 in Garland, Texas, two gunmen opened fire at a “draw the Prophet Muhammad” contest sponsored by the American Freedom Defense Initiative, listed as an extremist group by the Southern Poverty Law Center. Police shot and killed the two gunmen. A security guard was injured. Most Muslims consider images of the prophet highly offensive, as Islam prohibits them. The attack comes almost four months to the day that four cartoonists at the French weekly Charlie Hebdo were killed by extremists offended at the magazine’s satirical depictions of the prophet.

Why do images of the founder of Islam — even cartoons drawn by amateurs — incite so much anger in some people that they are motivated to violence?