While some other prominent leaders of irregulars in the Bleeding Kansas border conflict shared these traits, Jennison was distinguished by his blatant plunder for personal gain.

In command of nine men, Jennison "tried" and hanged Russell Hinds near the state line at Mine Creek for the offense of helping to return a fugitive slave to his master in Missouri.

[4] Hinds had rejected the standard $25 reward ($515 in 2005 dollars), but did accept $5 reimbursement for his expenses in transporting the slave, who had agreed to return to his master while awaiting legal emancipation.

The article reported Jennison as refusing to allow non-abolitionist soldiers to serve under his command, and asserting that "the slaves of [southerners] can always find a protection in... [my] camp, and they will be defended to the last man and bullet."

While the regiment was at Leavenworth, Kansas, in April 1862, Jennison, angered over James G. Blunt being named brigadier general in his stead, resigned from the army and turned to banditry as a Redleg.

[9] In a particularly egregious incident late in the war, Jennison shot and killed 66 year old civilian David Gregg "on the public highway north of Parkville [sic], Platte Co.