  We present imaging and spectral studies of the supernova remnant (SNR)
Sagittarius (Sgr) A East from deep observations with the {\it Chandra X-Ray
Observatory}. The spatially-resolved spectral analysis of Sgr A East reveals
the presence of a two-temperature thermal plasma ($kT$ $\sim$ 1 keV and 5 keV)
near the center of the SNR. The central region is dominated by emission from
highly-ionized Fe-rich ejecta. We estimate a conservative upper limit on the
total Fe ejecta mass of the SNR, M$_{Fe}$ $<$ 0.27 M$_{\odot}$. Comparisons
with standard SN nucleosynthesis models suggest that this Fe mass limit is
consistent with a Type II SN explosion for the origin of Sgr A East. On the
other hand, the soft X-ray emission extending toward the north of the SNR can
be described by a single-temperature ($kT$ $\sim$ 1.3 keV) thermal plasma with
normal chemical composition. This portion of the SNR is thus X-ray emission
from the heated interstellar medium rather than the metal-rich stellar ejecta.
We point out that a hard pointlike source CXOGC J174545.5$-$285829 (the
so-called ``cannonball'') at the northern edge of the SNR shows unusual X-ray
characteristics among other Galactic center sources. The morphological,
spectral, and temporal characteristics of this source suggest an identification
as a high-velocity neutron star. Based on the suggested Type II origin for the
SNR Sgr A East and the proximity between the two, we propose that CXOGC
J174545.5$-$285829 is a high-velocity neutron star candidate, born from the
core-collapse SN which also created the SNR Sgr A East.
