The scene doesn't apportion blame for the alleged bloodbath, but the mural gives more space to the violent, weapon-wielding Indians. The casual viewer will conclude they're the aggressors.
A page on the faux Pawnee website refers to a similar incident. It could be the same incident, but the lovers' genders are reversed. In any case, the website confirms the show's flippant attitude toward Indians. People killing each other over Euro-American imperialism...ha ha.
Wamapokestone Park was established in 1906 over the shared grave of a Wamapoke teen bride and the love of her life, an unknown White settler. Their story is like “Romeo and Juliet,” if Romeo had taken Juliet by force and Juliet’s father had then killed Romeo.
Amy Poehler, the creative force behind Parks and Recreation, is building quite a track record on Indians. Unfortunately, it isn't a positive one.
There are these incidents in the series:
Spirit of Pawnee in Parks and Recreation
Face-Cutting in Parks and Recreation
Twisted to Death in Parks and Recreation
Indians in Parks and Recreation
Her Palin rap during the 2008 presidential campaign:
Palin Rap Features "Eskimos"
And this picture of her in a hipster headdress:
I wonder if this is the liberal equivalent of the conservative view of Indians. She doesn't come out and call them "savages," "drunks," or "lazy bums." But she appears to believe the most common stereotypes. Judging by the evidence, she's no more informed than the average ignorant student.
She may think she's helping or "honoring" Indians by including them in her show. But her tone is condescending, along the lines of: "Look at those quaint, colorful characters with their strange customs and clothing." It's the unconscious racism of a Stephenie Meyer or Hollywood exec rather than the conscious racism of a Pat Buchanan or Jim Marino.
For more on the subject, see TV Shows Featuring Indians and US Report to the UN on Racism.