  The debris disk around $\beta$~Pictoris is known to contain gas. Previous
ALMA observations revealed a CO belt at $\sim$85 au with a distinct clump,
interpreted as a location of enhanced gas production. Photodissociation
converts CO into C and O within $\sim$50 years. We resolve CI emission at 492
GHz using ALMA and study its spatial distribution. CI shows the same clump as
seen for CO. This is surprising, as C is expected to quickly spread in azimuth.
We derive a low C mass (between $5\times10^{-4}$ and $3.1\times10^{-3}$
M$_\oplus$), indicating that gas production started only recently (within
$\sim$5000 years). No evidence is seen for an atomic accretion disk inwards of
the CO belt, perhaps because the gas did not yet have time to spread radially.
The fact that C and CO share the same asymmetry argues against a previously
proposed scenario where the clump is due to an outward migrating planet
trapping planetesimals in an resonance; nor can the observations be explained
by an eccentric planetesimal belt secularly forced by a planet. Instead, we
suggest that the dust and gas disks should be eccentric. Such a configuration,
we further speculate, might be produced by a recent tidal disruption event.
Assuming that the disrupted body has had a CO mass fraction of 10%, its total
mass would be $\gtrsim$3 $M_\mathrm{Moon}$.
