I have found a Summary of Zahn's latest film Por Vida. Now you can at
least try to imagine what Zahn's character Grim is going to be like
or even if there are any hints at which character mentioned in the
story he may be.

Source: http://www.actorsinsider.com/actor/viewpostad.aspx?id=39&loc=

STORY: On August 10, 2005, The New York Times published an article by
reporter Michael Winerip entitled Essays in Search of Happy Endings,
about a class at Locke High School in the Watts neighborhood of South-
Central Los Angeles. The students were assigned to write about a day
in their lives. The article featured the
essay of one student, Lesly Castillo, who at age 15 was running the
girl clique of a major Latino gang and dating the 24-year-old gang
leader.

After the article appeared, filmmaker Alan Jacobs (American Gun, Nina
Takes a Lover) acquired the film rights from The New York Times,
secured the life rights from Lesly Castillo, and developed a
screenplay inspired by the real-life events. Like the essay, POR VIDA
takes place all in one day—the day that the 15-year-old girl, Rascal,
decides to leave the gang. Leaving, she discovers, is a good deal
harder than joining.

Rascal's story is further complicated by racial tensions between her
Latina gang and a rival black girl gang, a frequent problem today in
South-Central Los Angeles schools. The screenplay presents a raw,
authentic look at a teenager's life in the ghetto. Some have compared
it to the hit Denzel Washington film Training Day in that
it compresses an entire world into a single, dramatic day. Others
liken it to the Brazilian hit film City of God for its unflinching
look at a world most of us know little about.

Because of the project's social significance, the screenplay quality,
and the director's track record, POR VIDA has the makings of a
Sundance 'buzz movie' and the potential to attract positive media
attention, giving everyone involved the opportunity to participate in
something special.