While teaching German at Harvard University he poisoned his pregnant wife, but he fled before this was discovered and spent the next decade in various places throughout the United States under assumed identities.
On July 2, 1915, Muenter hid a package containing three sticks of dynamite with a timing mechanism set for nearly midnight under a telephone switchboard in the Senate reception room in the United States Capitol, Washington, D.C. His original target had been the Senate chamber, which he found locked. The bomb exploded at approximately 11:40 PM resulting in no casualties. Muenter wrote a letter to The Washington Star under an pseudonym explaining his actions that was published after the bombing, in it he said he hoped the explosion would "make enough noise to be heard above the voices that clamor for war. This explosion is an exclamation point in my appeal for peace."
After setting off the bomb in the Capitol, he fled to New York City, where he hid a device on the SS Minnehaha, a ship which had been loaded with munitions bound for Britain, and then made his way to the home of American financier J. P. Morgan, Jr.. Muenter was also angry with those who were aiding Great Britain against Germany in World War I, in particular Morgan. Muenter shot Morgan twice in the groin at Morgan's house in Glen Cove, New York. Muenter was thwarted and captured in this attack. He was charged with both assaults and soon after committed suicide while in prison. On July 7, just two days after his jail cell suicide, the device he had planted on the Minnehaha exploded, though it had been placed far away from the munitions, and the resulting fire only caused minor damage.
- "Chas. Apted Dies; 'Cop' at Harvard". New York Times. June 6, 1941. p. 21.
- Russell, Daniel E. "The Day Morgan Was Shot". Glen Cove Heritage.[better source needed]
- "Man Who Shot J. P. Morgan Twice Admits Setting Bomb At National Capital". Hartford Courant. July 4, 1915. Retrieved 2009-10-30. "Former German Instructor At Cornell Talks Freely After Third Degree Is Used, and Says He Wanted To Stop Shipment of Munitions To Europe. Is Suspected of Other, Similar Crimes. Describes Construction of Rare Type of 'Infernal Machine'. Financier Reported in Excellent Condition. Has Two Bullet Wounds In His Hip."
- "Bomb Rocks Capitol". United States Senate. Retrieved 19 May 2013.
- Kinghorn, Jonathan. "S.S. Minnehaha". The Atlantic Transport Line. Retrieved 14 June 2014.