  Gravitational waves from $\sim 90$ black holes binary systems have currently
been detected by the LIGO and Virgo experiments, and their progenitors'
properties inferred. This allowed the scientific community to draw conclusions
on the formation channels of black holes in binaries, informing population
models and -- at times -- defying our understanding of black hole astrophysics.
The most challenging event detected so far is the short duration
gravitational-wave transient GW190521. We analyze this signal under the
hypothesis that it was generated by the merger of two nonspinning black holes
on hyperbolic orbits. The best configuration matching the data corresponds to
two black holes of source frame masses of $81^{+62}_{-25}M_\odot$ and
$52^{+32}_{-32}M_\odot$ undergoing two encounters and then merging into an
intermediate-mass black hole. We find that the hyperbolic merger hypothesis is
favored with respect to a quasi-circular merger with precessing spins with
Bayes' factors larger than 4300 to 1, although this number will be reduced by
the currently uncertain prior odds. Our results suggest that GW190521 might be
the first gravitational-wave detection from the dynamical capture of two
stellar-mass nonspinning black holes.
